Films made of a syndiotactic polystyrene resin composition (syndiotactic polystyrene films) have excellent heat resistance, chemical resistance, hot water resistance, dielectric characteristics, electrical insulation, etc., and thus are expected to be used in various applications. In particular, for their excellent dielectric characteristics together with high electrical insulation and heat resistance, they are expected to be used as insulators for capacitors (Patent Documents 1 and 2). Then, further improvements have been made, and techniques related to syndiotactic polystyrene films for use in capacitor applications have been disclosed. For example, Patent Document 3 discloses a technique for improving withstand voltage by suppressing impurities in a film, Patent Document 4 discloses a technique for improving handling properties and wear resistance by adjusting particles added, etc., and Patent Documents 5 and 6 disclose a technique for reducing thickness variations by adjusting the refractive index of a film. In addition, Patent Document 7 discloses a technique for improving breakdown voltage by adding an antioxidant.    (Patent Document 1) JP-A-1-182346    (Patent Document 2) JP-A-1-316246    (Patent Document 3) JP-A-3-124750    (Patent Document 4) JP-A-6-80793    (Patent Document 5) JP-A-7-156263    (Patent Document 6) JP-A-8-283496    (Patent Document 7) JP-A-2009-235321